The American Association for the Advancement of Science: American nuclear industry may have a future yet

THE NUCLEAR industry in the US is down but not out. At least, not if
the Advanced Light Water Reactor (ALWR) Program comes to anything. John
Taylor, a scientist from the Electric Power Research Institute in California,
described the industry’s attempts to design reactors that are safer, simpler
and cheaper than existing models. The idea is also to produce standardised
designs that do not become bogged down in the licensing process.

Taylor and his colleagues also run the programme to clean up the reactor
at Three Mile Island that was wrecked in an accident in 1979. Taylor blamed
many of today’s problems on the competition between designers and reactor
makers in the early days of nuclear power. This, he said, ‘resulted in rapidly
increased sizes, reduced engineering margins, and greater system complexity’.

As a consequence, he said, ‘the biggest problems we face in operating
our nuclear plants are ones based on human performance’. ‘It is simply unnecessarily
difficult to operate and maintain the complex and individually-designed
plants we have in operation today,’ he added.

The nuclear industry is not just worried about human safety, however.
It is also keen to reduce the risks to capital invested in reactors. As
Taylor put it: ‘Utilities have a special interest in safety to property,
which we are trying to emphasise in the ALWR Program to the benefit, we
believe, of the public’s safety as well.’

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The ALWR programme has produced initial designs for reactors with cooling
systems that will continue to operate no matter what happens in an accident.
There are two types of design for both boiling-water reactors (BWRs) and
pressurised-water reactors (PWRs). The proposed ‘passive’ plants would work
under natural circulation even during normal operation; the ‘evolutionary’
designs would use pumps during normal operation but natural circulation
would remove heat in the event of an accident.

The evolutionary reactors would be the same size as modern reactors,
producing 1200 megawatts, while the passive designs would produce 600 MW.
The US Department of Energy recently awarded both General Electric (GE)
and Westinghouse contracts worth $50 million each to develop the designs
for passive PWRs and BWRs.

GE has advanced the idea of a simplified boiling water reactor (SWBR)
that will operate under natural circulation, even at full power. ‘That is,
it will not require pumps to circulate the water through the core in the
process of generating steam to turn the turbine and make electricity. Second,
when the reactor is shut down the core will be kept cool by introducing
natural circulation through gravity drain of water from elevated water tanks.’

It is not possible to design a PWR that works with natural cooling at
full power, so in normal operation, pumps would maintain the flow of water.
‘In the emergency condition when an accident could cause a loss of normal
coolant, the core is kept cool by a combination of tanks of water with nitrogen
pressure . . . to drive the water into the system, and elevated tanks which
supply water by gravity drain.’

The idea is to produce a reactor that can continue to cool itself without
the operators having to do anything. In the case of the new passive PWR,
Taylor claims that the emergency cooling system will continue to operate
for three days after an accident, even if the operators sit back and do
nothing.